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revng-revng/include/revng-c/RestructureCFG/ASTTree.h
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Andrea Gussoni 733f5008b3 BeautifyGHAST: implement DualSwitch simplify
We introduce a simplification step, which looks for `switch`es that can
be reduced to simpler `if` statements.

Specifically, the logic is the following:
1) When we identify a `switch` statement composed by a single `case` and
   a possible default, we transform it into an `if` with the `case` now
   corresponding to the `then`, and the `default` corresponding to the
   `else`, if present.
2) When we identify a `switch` statement composed by two `case`s, and no
   `default` is present, we can promote it to an `if` with `then` `else`
   branches.

Other key details:
- The promotion happens only if we can identify at least one of the
  `case`s that have a single element in the `case` label. If this is not
  the case, we do not promote one to RHS of the `if` condition.
- A new `CompareNode` class, inheriting from `ExprNode`, is created, in
  order to represent the equality or inequality condition of an `IfNode`
  instance that is the result of the promotion. This `CompareNode` can
  represent for the LHS both an `llvm::Value` or the `loop_state_var`,
  while it embeds the RHS constant which completes the comparison.
- We remove `SwitchBreak` AST nodes that may now appear as children of
  an `if` node promoted from a `switch`.
- We introduce in the `CompareNode` the `weaved` concept. Indeed, if a
  promotion of a weaved `switch` happens, we should avoid the
  serialization of the instructions leading to the computation of the
  condition of the original `switch`, because they have been already
  emitted by the main related dominating `switch`.

We also introduce an additional simplification step, which takes care
of:
- Promoting `!(==)` to `(!=)` and `!(!=)` to `(==)`, if the inner
  equal/not equal is represented via a `CompareNode`.
- Promoting `x == 0` to `!x` and `x != 0` to `x`.

To be able to correctly emit (or not) the instructions computing a
condition of an `IfNode`, we need to add the `EmittBB` flag, an
additional parameter to the `buildGHASTCondition` function, which
controls the emission of the statements of a basic block computing a
condition.

Consequently, the `IfNode` acquires a `IsWeaved` field, which is used to
mirror the property having the same name on `SwitchNode`. Being now
possible a promotion from a dual `SwitchNode` to an `IfNode`, we need to
represent this property on the `IfNode` too.
2023-10-23 18:16:20 +02:00

131 lines
3.8 KiB
C++

#pragma once
//
// Copyright rev.ng Labs Srl. See LICENSE.md for details.
//
#include <cstdlib>
#include <type_traits>
#include "revng-c/RestructureCFG/ASTNode.h"
// Forward declarations.
class ASTNode;
template<class NodeT>
class BasicBlockNode;
class SequenceNode;
class ASTTree {
public:
using ast_deleter_t = decltype(&ASTNode::deleteASTNode);
using ast_destructor = std::integral_constant<ast_deleter_t,
&ASTNode::deleteASTNode>;
using ast_unique_ptr = std::unique_ptr<ASTNode, ast_destructor>;
using getPointerT = ASTNode *(*) (ast_unique_ptr &);
static ASTNode *getPointer(ast_unique_ptr &Original) {
return Original.get();
}
static_assert(std::is_same_v<decltype(&getPointer), getPointerT>);
using links_container = std::vector<ast_unique_ptr>;
using internal_iterator = typename links_container::iterator;
using links_iterator = llvm::mapped_iterator<internal_iterator, getPointerT>;
using links_range = llvm::iterator_range<links_iterator>;
using expr_deleter_t = decltype(&ExprNode::deleteExprNode);
using expr_destructor = std::integral_constant<expr_deleter_t,
&ExprNode::deleteExprNode>;
using expr_unique_ptr = std::unique_ptr<ExprNode, expr_destructor>;
using links_container_expr = std::vector<expr_unique_ptr>;
using links_iterator_expr = typename links_container_expr::iterator;
using links_range_expr = llvm::iterator_range<links_iterator_expr>;
using ASTNodeMap = ASTNode::ASTNodeMap;
using BasicBlockNodeBB = ASTNode::BasicBlockNodeBB;
using BBNodeMap = ASTNode::BBNodeMap;
links_iterator begin() {
return llvm::map_iterator(ASTNodeList.begin(), getPointer);
}
links_iterator end() {
return llvm::map_iterator(ASTNodeList.end(), getPointer);
}
links_iterator_expr beginExpr() { return CondExprList.begin(); }
links_iterator_expr endExpr() { return CondExprList.end(); }
private:
links_container ASTNodeList = {};
std::map<BasicBlockNodeBB *, ASTNode *> BBASTMap = {};
std::map<ASTNode *, BasicBlockNodeBB *> ASTBBMap = {};
ASTNode *RootNode = nullptr;
unsigned IDCounter = 0;
links_container_expr CondExprList = {};
public:
ASTTree() = default;
// Default movable
ASTTree(ASTTree &&) = default;
ASTTree &operator=(ASTTree &&) = default;
// Non copyable
ASTTree(const ASTTree &) = delete;
ASTTree &operator=(const ASTTree &) = delete;
private:
ASTNode *addASTNodeImpl(ast_unique_ptr &&ASTObject);
public:
SequenceNode *addSequenceNode();
SwitchBreakNode *addSwitchBreak(SwitchNode *SN);
unsigned getNewID() { return IDCounter++; }
links_range nodes() { return llvm::make_range(begin(), end()); }
links_range_expr expressions() {
return llvm::make_range(beginExpr(), endExpr());
}
links_container::size_type size() const;
void addASTNode(BasicBlockNodeBB *Node, ast_unique_ptr &&ASTObject);
ASTNode *addASTNode(ast_unique_ptr &&ASTObject);
void removeASTNode(ASTNode *Node);
ASTNode *findASTNode(BasicBlockNodeBB *BlockNode);
BasicBlockNodeBB *findCFGNode(ASTNode *Node);
void setRoot(ASTNode *Root);
ASTNode *getRoot() const;
ASTNode *copyASTNodesFrom(ASTTree &OldAST);
/// Dump a GraphViz file on a file using an absolute path
debug_function void dumpASTOnFile(const std::string &FileName) const;
/// Dump a GraphViz file on a file using an absolute path
debug_function void dumpASTOnFile(const char *FName) const {
return dumpASTOnFile(std::string(FName));
}
/// Dump a GraphViz file on a file representing this function
debug_function void dumpASTOnFile(const std::string &FolderName,
const std::string &FunctionName,
const std::string &FileName) const;
ExprNode *addCondExpr(expr_unique_ptr &&Expr);
};